Pressure actuated switch



Patented Oct. 12, 1 943 "*U lTEo STATES PATENT orrics I 2,331,826 PRESSURE ACTUATED swrcrcu Edwin B. Davenport, San Francisco, Calif. Application June23, 1941, Serial No. 399,278

sci ims. (crew-s3) T .Thezpresent invention relates to pressure actuated electric switchessuitable for automatic control of the ignition-circuit of an internal combustionengine. I

- The-proper function clan internal combustion engine sometimes :depends upon fluid pressure, such, for example, .as thegpress'ure of .oil in its lubricating system or the premure of a fluidat the discharged side of a pump propelled by the engine.

invention is, particularly intended for combination with any engine and a pump propolled thereby, though it maybe used in connection with any .fluid whereit is desired that the pressure-of the :fiuid control theoperation .of an electric switch for any P se.

;-Oneexample ot a-useful function'ofthe inventlon is in the case :of a pump propelled by an internal combustion engine :for pump water from a well' or stream for irrigation purposes or thelike. Often :the water pumped in this manner servesto lubricatethe pump, and a part of the-water is bypassed to the, cooling systemic! thelenginet In the event of any failure on the suction side of the pump-which interrupts :the flow of water thereto, the pumpand engine may suflerconsiderable damage unless the engine is s opped. The obdect oi the present invention; is, therefore, to provide a simple positive acting switch and pressure actuated control for the switch. by means of which an internal combustron engine may. be stopped immediately and automtically by a drop of pressure: in a-fluid A furtherobiest of the invention is. to provide 11128 1011 a deviccmeans toset the switch manually tor starting of theengine during lowpressure conditions in the fluid circuit, and automatically toset the switch. to its-normai-running positibnas thepressure in the circuit, goes up after the-engine hasbeen started.

Further objects and advantages of theqengine are made apparent in. the; following specification wherein reference is made to the accompanying drawing which illustratesa. preferred form of the invention. In the'draw-ing' I Fig. 1 is a central vertical section of aswitch embodying thepresentinvention,and showing the position-oi the parts assumed during. low pressure conditions;

Fig. 2 is a similar view illustrating the position assumed bythexpantsof the switch under high pressure conditions;

Fig. 3 is a similar view of the switch with the parts shown in their manually controlled starting position;

Fig. 4 is asectionitaken on'line IV-IVoi Fig.1; and

Fig. 515 aviewrsimilar toliigs. i1.-and'2;illliltrsting a modified: form of the invention.

Referring to thedrawing indetailzthe switcher! the present invention :is gshownns comprising a generally cylindrical body member 10,:theupnr end of which lie covered by a nap :tl :tormedatc provideabove the bodymemioeraswitchchanrhr l2. The cap H is formed out :nfiy \s'mtnblent electric material, 101' 'iLueite,.f ivhich: he been found very satistactory tor this The capmay be retainedionzthe bodyxmemmr .lvl bymeans ofaeet screw-assmwnatztii. bottom of thebodymemberzifl aplaterimis-secmnd as by screws ii to form a pressure-:chamberi l6 and to retain in ,place in said chamber :a phragrn l-I. Theiplate M is bored'andithrmfid toreeeive a pipe l8 or etherzfittinguby nieanstod which the pressure chamber :may' .bezplaced in communication with 1a; fluidcircinmsuch .as ".the discharge ofapump-or flnc-waterjaclret .0: other fitting in coolingsystem of an engine. The chamber in contains a pair of resilbt contact fingers ll, each-of which preferably or; tendsaeross the top .611 the clunnber,r and is.bent downwardly and back :towardits endywhinh is bent at a right angietoprudentin *a'. directlm generally toward themailer of the chamlmt. Eachot these contacts fingers 26 ksecm'edas hp solder, indicatedeaitill, to a vtiremll. .occnpies a :bore flex-tendinglongitudinally or the cylindrical-sidewall oi -the cap; ea-enact the wires 22 abindingapestldenters thessifle will ul! the capthrouglea bore whichimteroepis theilnnu 23 andithe inner endrofithe bindinmpostvisiiirmm' versely drilled toreceive-thewire-iZi; .A-nut'i onthe-bindingipostis tightenedagainst the mm waillaof the-cap toiretain' it ingplace; amid admin. is employed:to-clamp theltermixiu's oflaawire'l'kiri' place. The binding post ;is preferably. formed as an ordinary machine 'SGr8W,' S0"UhMl"thB".hM thereofiprevents removal: of the clampingi nut 20 when it-isloosenedrtoaeileasethd wire Tl. A-p'osti 28* is arrangediconcentricallyof the chamber and extends .upwardlyi through theitop of thezcliamber to provide a ,push'button w by'meansi of which iii may be manually movedifnom themlliended tionillustrated in 11 to-the depressedipa'sitlbn illustrated inFla. 3; andiavspringzpressedudetenii 3.0acts'withua pair oil grooves 'formeduin the post to retain it in either of the two positions illustrated. The post 28 carries a stop collar 3| which limits its upward movement, and a contact collar 32 positioned to engage the ends of the contact stopped. In-the structure shown each of the wires 21 is intended to lead to the primary wire of one of the cylinders of a two cylinder engine,

consequently, if the parts are in the position 11- lustrated in Fig. 1 the primary circuit oi. the engine is grounded through the wires 21, wires 22, contact fingers 20 and collar-32 of the post 28, which post carries a spring 33, which ensures completion of the circuit to the body of the switch and to the ground.

;To break the circuit to the ground while the engine is running and while pressure is maintained in. the pressure chamber I6 the body member I is centrally bored and provided with a... hollow plunger 34, the lower end of which is closed by an. enlarged head 35 which rests against. the diaphragm. I1. The plunger 34 is urged downwardly by a spring 38interposed between the head 35 and-a nut 31, which serves asa guide for the upper end 01. the plunger. The

" upper .end of the plunger carries a cup 38 of dielectric material, which is provided with a hollow downwardly extending stem, which serves to support it with relation to the plunger and also servesto guide thelower end of the post 28.

.During operation of the engine, which is accompanied by high pressure on the pressure side ofthe pump withwhich the chamber communicates, the diaphragm-i1 is held in its uppermost position as illustrated in Fig. 2, and holds theplunger 34 in a position where the cup 38, carried by its upper end, surrounds the contact collar 32, and engages the ends of the contactfingers 20 holding them out of contact with the collar thus holding the circuit to the ground open. The parts remain in this position throughout the continued satisfactory operation ofthe .engine and pump, but upon any failure of the pump to deliverfiuid, the pressure at its discharge end and consequently in the chamber I6- drops, permitting the grounding switch to as-' sume the closed-position illustrated in Fig. 1.

..As. it isimpossible to start the engine with its ignition grounded the button 29 is depressed for starting, causing the parts to assume the position illustrated in Fig. '3 wherein the contact collar 32 has been moved down into the cup 38 leaving'the contact fingers 20 supported on the edges of the cupwith the circuit broken. With the. switch in this position the engine may be started and, assuming the pump to be functioning properly, pressure will immediately be built up in the chamber I6 again to raise the plunger to the position illustrated-in Fig. 2. As the contact co1lar32 rests on'the bottom of the cup, the post 28 will be raised by the plunger to return the push button 29 automatically to its normal running position shown in Fig. 2.

.It is-possible that the diaphragm I! may at its lowest position contact the bottom of the shailowpressure chamber [6 and close the orilustrated in Fig. 5 may be employed.

fice which forms the communication between the source of pressure and the chamber. This would greatly reduce the area of the diaphragm subjected to pressure and prevent proper operation of the plunger except in the event of very high pressures. To insure admission of pressure to the entire areaof the diaphragm the bottom of the chamber I6 is provided with a plurality of radial grooves as shown in Fig. 1 at 16a to admit pressure to the chamber even though its centered orifice may be obstructed by the diaph'ragm.

'In the case of some engines it is desirable to break an ignition circuit rather than to ground the circuit for stopping the engine, and for this purpose the modified form of the invention ii- In this modification the plunger 34 is of solid construction and is formed with a cup 40 of conducting material at its .upper end. A push button ll with a collar 42 at its lower end is formed of a di-electric material and preferably bored to receive a guide post 43, which extends upwardly from the plunger. In this case the contact fingers 20 are included as a part of a single circuit and arebridged to close the circuit by the cup 40. The operation of this modification is identical with that described above, though the result in connection with the switch is reversed as the switch is closed when the plunger is raised by pressure as shown in Fig. 5, and opened when the pressure drops and the plunger recedes to permit the contact fingers to be supported in spaced relationship on the di-electric collar 42.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a pressure actuated switch a resilient contact finger, a reciprocable post having a projection engaging said finger to complete a circuit, and a pressure actuated plunger concentric with said post and carrying a cup shaped dielectric member to embrace said projection and 'raise said contact finger out of engagement with said post and carrying a cup shaped dielectric member to embrace said projection and raise said contact finger out of engagement therewith under influence of high pressure, and means to depress said post to cause'said projection to enter the cup shaped member when the plungerhas receded during low pressure conditions.

3.. In a pressure actuated switch, a switch chamber, a pair of resilient contact members therein, a reciprocable post having a conducting collar engageable with said members, a normally retracted pressure actuated plunger entering the chamber from one end and concentric with said post, a di-electric cup carried by said plunger to embrace the collar 'on the post and separate the contact members therefrom when the plunger is "advanced, and means to depress the ost manually to cause the collar to enter the cup while the plunger is retracted.

EDWIN DAVENPORT. 

